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Abstract:

A vehicle includes sidewalls, a tailgate located proximate to rear ends
of the sidewalls, and a tailgate energy management system. The tailgate
energy management system includes a governor coupled to one of the
sidewalls and to the tailgate. The governor selectively applies a
governing force to the tailgate to reduce an opening speed of the
tailgate. The tailgate energy management system also includes a speed
sensor sensing an opening speed of the tailgate and an electronic control
unit electronically coupled to the governor and the speed sensor. The
electronic control unit includes a processor and memory storing an
instruction set. The electronic control unit receives a speed signal
indicative of the opening speed of the tailgate and the processor
executes the instruction set to cause the electronic control unit to
transmit a control signal to the governor to slow the opening speed of
the tailgate based on the speed signal.

Claims:

1. A method of managing remote actuation of a vehicle tailgate
comprising: receiving a command to open the tailgate; transmitting an
unlatch signal to at least one tailgate latch actuator to unlatch the
tailgate latch from a corresponding tailgate latch striker; applying an
unlatch force to the tailgate latch that is smaller than a predetermined
maximum unlatch force.

2. The method of managing remote actuation of the vehicle tailgate of
claim 1, further comprising terminating the unlatch signal to the at
least one tailgate latch actuator if an external load applied to the
tailgate is greater than an predetermined maximum external load.

3. The method of managing remote actuation of the vehicle tailgate of
claim 1, wherein the tailgate latch actuator applies an unlatch force to
the tailgate latch.

4. The method of managing remote actuation of the vehicle tailgate of
claim 1, wherein the unlatch force applied by the tailgate latch actuator
to the latch is greater than an internal resistance of the tailgate
latch.

5. The method of managing remote actuation of the vehicle tailgate of
claim 5, wherein the external load applied to the tailgate latch
increases an internal resistance of the tailgate latch.

6. The method of managing remote actuation of the vehicle tailgate of
claim 5, wherein the unlatch force applied by the tailgate latch actuator
to the latch is greater than the internal resistance of the tailgate
latch when an external load less than the predetermined maximum external
load is applied to the tailgate.

7. The method of managing remote actuation of the vehicle tailgate of
claim 6, wherein the unlatch force applied to the tailgate latch actuator
is less than the internal resistance of the tailgate latch when an
external load greater than the maximum external load is applied to the
tailgate.

8. A vehicle comprising: a tailgate latch coupled to one of a vehicle
tailgate or sidewalls of a vehicle; a tailgate latch striker coupled to
one of the vehicle tailgate or sidewalls of the vehicle, the tailgate
latch and the tailgate latch striker positioned to selectively latch with
one another; a tailgate latch actuator coupled to the tailgate latch that
selectively applies an unlatch force to the tailgate latch, the unlatch
force being smaller than a predetermined maximum latch force that
corresponds to a predetermined maximum external load applied to the
tailgate; and a command device communicatively coupled to the tailgate
latch actuator, the command device configured to provide an unlatch
signal to the tailgate latch actuator.

9. The vehicle of claim 8, wherein if the external load applied to the
tailgate is greater than the predetermined maximum external load, the
tailgate latch remains latched to the tailgate latch striker.

10. The vehicle of claim 8, further comprising an electronic control unit
communicatively coupled to the tailgate latch actuator, the electronic
control unit comprising a processor and a memory storing a computer
readable instruction set that, when executed by the processor, receives
the unlatch signal from the command device and transmits a signal to the
tailgate latch actuator to apply the unlatch force to the tailgate latch.

11. The vehicle of claim 10 further comprising a governor coupled to one
of the sidewalls and to the tailgate, the governor selectively applying a
governing force to the tailgate to reduce an opening speed of the
tailgate.

12. The vehicle of claim 11 further comprising a speed sensor
communicatively coupled to the electronic control unit sensing the
opening speed of the tailgate, wherein the electronic control unit
receives a speed signal indicative of the opening speed of the tailgate
from the speed sensor and the processor executes the instruction set to
cause the electronic control unit to transmit a control signal to the
governor such that the governor slows the opening speed of the tailgate
based on the speed signal.

13. The vehicle of claim 8, wherein the command device comprises a
wireless receiver communicatively coupled to the electronic control unit,
the radio receiver receives a wireless command signal to open the
tailgate, the wireless receiver relays the wireless command signal to
tailgate latch actuator to command the tailgate latch actuator to apply
the unlatch force to the tailgate latch.

[0003] Vehicles having deployable tailgates, for example, pickup trucks,
passenger vans, and sport utility vehicles (SUVs), may include lift
assist devices that reduce the amount of force required to be applied by
a user to control the motion of the tailgates as they are moved between
open and closed positions. The lift assist devices may include gas
dampers and/or torsion springs that apply a direction force to the
tailgate that allows for easier opening and/or closing of the tailgate.

[0004] However, lift assist devices may not apply a force of variable
intensity to accommodate a variety of conditions that the vehicle may be
subject to. Using a pickup truck as an example, the opening speed (and
therefore opening energy) of a tailgate may vary depending on vehicle
inclination, ambient temperature, and/or gas damper wear. The variability
in opening energy may be problematic in applications where the user
chooses to open a tailgate while at a remote location, for example, when
using a remote keyless entry system. In such an application, tailgates
that contact surrounding objects while opening with energy greater than a
predefined threshold energy may cause damage to the tailgate and/or the
surrounding object.

[0006] In one embodiment, a vehicle includes sidewalls spaced laterally
apart from one another, a tailgate located proximate to rear ends of the
sidewalls, and a governor coupled to one of the sidewalls and to the
tailgate. The governor selectively applies a governing force to the
tailgate to reduce an opening speed of the tailgate. The vehicle also
includes a speed sensor sensing an opening speed of the tailgate and an
electronic control unit electronically coupled to the governor and the
speed sensor. The electronic control unit includes a processor and memory
storing a computer readable and executable instruction set. The
electronic control unit receives a speed signal indicative of the opening
speed of the tailgate from the speed sensor and the processor executes
the instruction set to cause the electronic control unit to transmit a
control signal to the governor such that the governor slows the opening
speed of the tailgate based on the speed signal.

[0007] In another embodiment, a vehicle includes sidewalls spaced
laterally apart from one another, a tailgate located proximate to rear
ends of the sidewalls, and a retractable cable assembly having a cable
coupled to the tailgate and a rotatable drum about which the cable is
wound. The vehicle also includes a governor coupled to the sidewalls and
to the rotatable drum, where the governor selectively applies a governing
force to the tailgate through the rotatable drum to slow an opening speed
of the tailgate.

[0008] In yet another embodiment, a tailgate energy management system for
controlling an opening speed of a tailgate relative to sidewalls of a
vehicle includes a governor coupled to one of the sidewalls and to the
tailgate, where the governor selectively applies a governing force to the
tailgate that reduce the opening speed of the tailgate. The tailgate
energy management system also includes a speed sensor sensing an opening
speed of the tailgate and an electronic control unit electronically
coupled to the governor and the speed sensor. The electronic control unit
includes a processor and memory storing a computer readable and
executable instruction set. The electronic control unit receives a speed
signal indicative of the opening speed of the tailgate from the speed
sensor and the processor executes the instruction set to cause the
electronic control unit to transmit a control signal to the governor such
that the governor slows the opening speed of the tailgate based on the
speed signal.

[0009] These and additional features provided by the embodiments described
herein will be more fully understood in view of the following detailed
description, in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The embodiments set forth in the drawings are illustrative and
exemplary in nature and not intended to limit the subject matter defined
by the claims. The following detailed description of the illustrative
embodiments can be understood when read in conjunction with the following
drawings, where like structure is indicated with like reference numerals
and in which:

[0011]FIG. 1 depicts a perspective view of a vehicle including a tailgate
energy management system according to one or more embodiments shown and
described herein;

[0012] FIG. 2 depicts a cut-away side view of a vehicle including a
tailgate energy management system according to one or more embodiments
shown and described herein;

[0013]FIG. 3 depicts a rear view of the vehicle including a tailgate
energy management system of FIG. 2 along line A-A;

[0014]FIG. 4 depicts a rear view of the tailgate energy management system
of FIG. 2 along line B-B;

[0015] FIG. 5 depicts a cut-away side view of a vehicle including a
tailgate energy management system according to one or more embodiments
shown and described herein;

[0016] FIG. 6 depicts a rear view of the vehicle including a tailgate
energy management system of FIG. 5 along line C-C;

[0017]FIG. 7 depicts a side view of a vehicle including a tailgate energy
management system according to one or more embodiments shown and
described herein; and

[0018] FIG. 8 depicts a cut-away side view of a vehicle including a
tailgate energy management system according to one or more embodiments
shown and described herein.

DETAILED DESCRIPTION

[0019] Embodiments described herein relate to vehicles having tailgate
energy management systems that limit the opening energy of the tailgates.
Referring to FIG. 1, one embodiment of a vehicle with a tailgate energy
management system is schematically depicted. The vehicle includes a
tailgate located proximate to the rear ends of the sidewalls of the
vehicle. A governor is coupled to one of the sidewalls and to the
tailgate. An electronic control unit works in conjunction with the
governor to selectively apply a governing force to the tailgate. The
governing force reduces the opening speed of the tailgate. The electronic
control unit receives a speed signal from a speed sensor that indicates
the opening speed of the tailgate. The electronic control unit transmits
a control signal to the governor causing the governor to apply the
governing force to the tailgate based on the speed signal. Embodiments of
the tailgate energy management system and vehicles incorporating the same
will be described in more detail herein.

[0020] Referring now to FIG. 1, one embodiment of a vehicle 80 including a
tailgate energy management system 100 is shown. The vehicle 80 includes
two sidewalls 92 spaced laterally apart from one another. A tailgate 90,
illustrated in an open position, is located proximate to the rear ends 93
of the sidewalls 92. The tailgate energy management system 100 includes a
governor 110 coupled to one of the sidewalls 92 of the vehicle 80. The
tailgate energy management system 100 also includes an electronic control
unit 200 electronically coupled to the governor 110 and to a speed sensor
210. The speed sensor 210 transmits a speed signal that is received by
the electronic control unit 200. The speed signal corresponds to the
opening speed of the tailgate 90. The speed sensor 210 may be a Hall
Effect sensor or a similar sensor for determining the rotational speed of
a component. The speed sensor 210 may determine the rotational rate of
the retractable cable assembly 120 or the linear speed of travel of the
cable 122 coupled to the tailgate 90.

[0021] As used herein, governor 110 is a clutch assembly or a brake
assembly that applies a force to a proximate component of the tailgate
energy management system 100 to slow or stop the movement of the
proximate component. In the embodiment described herein, the governor 110
is electronically actuated by a control signal transmitted from the
electronic control unit 200 and received by the governor 110. When the
governor 110 receives the control signal from the electronic control unit
200, the governor 110 applies a force to the proximate component of the
tailgate energy management system 100 such that the force reduces the
opening speed of the tailgate 90. An example of such an electronically
actuated governor 110 is an electromagnetic clutch or electromagnetic
brake available from Ogura Industrial Corp. of Somerset, N.J. In the
alternative, the governor 110 may be mechanically controlled and
actuated. Examples of such a mechanically controlled and actuated
governor 110 may include a centrifugal clutch or brake that engages a
proximate component of the tailgate energy management system 100 when the
speed of rotation of the centrifugal clutch or brake exceeds a threshold
speed.

[0022] In the embodiment depicted in FIG. 1, the tailgate energy
management system 100 further includes a retractable cable assembly 120
that includes a cable 122 and a rotatable drum 124. The cable 122 is
coupled to the tailgate 90 and is wound about the rotatable drum 124. The
rotatable drum 124 pays out the cable 122 as the tailgate 90 rotates from
a closed position (as depicted in FIG. 7) to an open position (as
depicted in FIG. 1). Additionally, the rotatable drum 124 collects the
cable 122 and winds the cable 122 about the rotatable drum 124 as the
tailgate 90 rotates from an open position to a closed position.

[0023] The vehicle 80 may also include an over-travel cable 96 coupled to
both the sidewall 92 and to the tailgate 90. The over-travel cable 96
supports the tailgate 90 when the tailgate 90 is in the open position and
stops the tailgate 90 from rotating. As shown in FIG. 1, the over-travel
cable 96 stops the tailgate 90 from rotating and holds the tailgate 90 in
an approximately horizontal orientation.

[0024] The vehicle 80 also includes at least one tailgate latch 70 and a
corresponding tailgate latch striker 72. The vehicle 80 depicted in FIG.
1 includes two tailgate latches 70 positioned along opposite sides of the
tailgate 90 proximate to each of the sidewalls 92. When the tailgate 90
is located in the closed position, the tailgate latches 70 interface with
the tailgate latch striker 72, thereby securing the tailgate 90 to the
sidewalls 92 of the vehicle 80 and maintaining the tailgate 90 in a
closed position. The tailgate latches 70 and the tailgate latch strikers
72 maintain the tailgate 90 in the closed position until the tailgate
latches 70 are actuated to decouple from one another. While the
embodiment of FIG. 1 depicts the tailgate latch 70 as being positioned
along the tailgate 90 and the tailgate latch strikers 70 positioned along
the sidewalls 92 of the vehicle 80, it should be understood that the
relative positions of the tailgate latches 70 and the tailgate latch
strikers 72 with respect to the tailgate 90 and the sidewalls 92 of the
vehicle 80 may be modified without departing from the scope of this
disclosure.

[0025] Referring to FIG. 8, the tailgate latches 70 are actuated to
release themselves from the tailgate latch strikers 72, thereby releasing
the tailgate 90 from the closed position relative to the sidewalls 92 of
the vehicle 80. The tailgate latches 70 may be actuated by a variety of
methods including, for example and without limitation, manual actuation
of a remotely-located latch release or automated actuation, for example
actuated by a tailgate latch actuator 74. In the embodiment depicted in
FIG. 8, the tailgate latch actuator 74 is a linearly-acting actuator,
however, other embodiments of tailgate latch actuators are contemplated
including rotary-acting actuators. In some embodiments, the tailgate
latch actuator 74 may be coupled to the latch 70 through a force
transmission mechanism (not shown), for example a Bowden cable or a
linkage, thereby allowing the tailgate latch actuator 74 to be position
and oriented at various locations within the vehicle 80 while continuing
to provide force to actuate the tailgate latch 70. In some embodiments, a
single tailgate latch actuator 74 may be coupled to tailgate latches 70
positioned along opposite sides of the tailgate 90 (as depicted in FIG.
1), such that the single tailgate latch actuator 74 actuates both
tailgate latches 70.

[0026] As conventionally known, the tailgate latch 70 includes an internal
resistance that prevents the tailgate latch 70 from spontaneously
opening, thereby allowing the tailgate latch 70 from becoming disengaged
from the tailgate latch striker 72 unless so actuated. To release the
tailgate 90 from the closed position relative to the sidewalls 92 of the
vehicle 80, the tailgate latches 70 are selectively unlatched from the
tailgate latch strikers 72, thereby decoupling the tailgate latches 70
from the tailgate latch strikers 72. The tailgate latch actuator 74
applies an unlatching force to the tailgate latch 70 as to disengage the
tailgate latch 70 from the tailgate latch striker 72. The unlatching
force is greater than the internal resistance of the tailgate latch 70
such that the unlatching force overcomes the internal resistance of the
tailgate latch 70.

[0027] In some embodiments, the kinetic energy that the tailgate 90 opens
with may be increased with the addition of an external force and/or mass
applied to the tailgate 90 in a direction that the tailgate 90 opens from
the sidewalls 92 of the vehicle 80. In one example, such external load
may be applied to the tailgate 90 by cargo positioned within the bed of
the vehicle 80. As discussed hereinabove, the tailgate energy management
system 100 mitigates the kinetic energy with which the tailgate 90 opens.
Increasing the kinetic energy of the tailgate 90 through the addition of
an external force and/or mass may be undesired. Further, the increase in
kinetic energy of the tailgate 90 through the addition of external force
and/or mass may reduce the effectively of the components of the tailgate
energy management system 100 such that the tailgate energy management
system cannot reduce the kinetic energy of the tailgate 90 to a desired
level. Accordingly, components that prevent the tailgate 90 from opening
when an external load and/or mass is applied to the tailgate 90 may be
desired.

[0028] In some embodiments of the tailgate latch 70, the internal
resistance of the tailgate latch 70 may increase when an external force
and/or mass is applied to the tailgate 90. The external force and/or mass
applied to the tailgate 90 is reacted through the tailgate latch 70 and
the tailgate latch striker 72, thereby increasing the force applied by
the tailgate latch 70 onto the tailgate latch striker 72 in the opening
direction of the tailgate 90. This increase in force between the tailgate
latch 70 and the tailgate latch striker 72 may increase the internal
resistance of the tailgate latch 70. An increase in the internal
resistance of the tailgate latch 70 may require that the tailgate latch
actuator 74 applies an increased latch actuation force to release the
tailgate latch 70 from the tailgate latch striker 72. To prevent opening
of the tailgate 90 when an external force and/or mass is applied to the
tailgate 90 that exceeds a predetermined maximum external load applied to
the tailgate 90, the maximum latch actuation force of the tailgate latch
actuator 74 may be actively or passively controlled such that the
tailgate latch actuator 74 provides an unlatch force capable of
unlatching the tailgate latch 70 from the tailgate latch striker 72 when
no external force and/or mass is applied to the tailgate 90 and is not
capable of unlatching the tailgate latch 70 from the tailgate latch
striker 72 when an external force and/or mass is applied to the tailgate
90.

[0029] In some embodiments, an end-user of the vehicle 80 may provide a
command to command device 230 to open the tailgate 90. In some
embodiments, the command device 230 may be incorporated into the
electronic control unit 200. In other embodiments, the command device 230
may be incorporated into a secondary electronic control module (not
shown). In still other embodiments, the command device 230 may be a
relay, which may be communicatively isolated from the electronic control
unit 200. In some embodiments, the end-user may provide the command to
open the tailgate 90 by toggling a switch (not shown), for example, a
vehicle body or cabin-mounted switch, that is communicatively coupled to
the command device 230. In other embodiments, the end-user may provide
the command to open the tailgate 90 by depressing a button on a radio
transmitting device (not shown). The radio transmitting device provides a
wireless signal, which is received by a wireless receiver 220 that is
communicatively coupled to the command device 230.

[0030] After receiving the command to open the tailgate 90 from the
end-user, the command device 230 may provide an unlatch signal to the
tailgate latch actuator 74, thereby commanding the tailgate latch
actuator 74 to apply the unlatch force to the tailgate latch 70 as to
unlatch the tailgate latch 70 from the tailgate latch striker 72. As
described hereinabove, the tailgate latch actuator 74 provides an unlatch
force to the tailgate latch 70 that is smaller than a predetermined
maximum unlatch force. By applying an unlatch force that is less than the
predetermined maximum unlatch force, the tailgate latch actuator 74
unlatches the tailgate latch 70 from the tailgate latch striker 72 when
external force and/or mass is applied to the tailgate 90 is less than a
predetermined maximum external load, and does not unlatch the tailgate
latch 70 from the tailgate latch striker 72 when external force and/or
mass is applied to the tailgate 90 exceeds a predetermined maximum
external load.

[0031] The unlatch signal provided to the tailgate latch actuator 74 by
the command device 230 may be terminated if an external force and/or mass
is applied to the tailgate 90. In some embodiments, the command device
230 may provide the unlatch signal to the tailgate latch actuator 74 and
subsequently terminate the unlatch signal to the tailgate latch actuator
74, such that if the unlatch force applied to the tailgate latch 70 by
the tailgate latch actuator 74 does not overcome the internal resistance
of the tailgate latch 70, the tailgate 90 will remain in a closed
position. In other embodiments, the electronic control unit 200 may
determine that the tailgate 90 has not opened following an unlatching
operation by the tailgate latch actuator 74, for example by sensing no
speed signal from the speed sensor 210, as depicted in FIG. 1. The
electronic control unit 200 may terminate the unlatch signal to the
tailgate latch actuator 74. In some embodiments, the command device 230
may be configured to "time-out" the unlatch signal as to stop
transmitting the unlatch signal to the tailgate latch actuator 74 after a
pre-determined time. Embodiments of the vehicle 80 incorporating the
tailgate latch actuator 74 may passively manage remote actuation of the
vehicle tailgate 90 by restricting remote actuation. As such, the
tailgate latch actuator 74 that manages remote actuation of the vehicle
tailgate 90 as to control remote actuation of the vehicle tailgate 90 may
do so without the inclusion of sensors to determine if an external force
and/or mass exceeding a predetermined maximum external load is applied to
the vehicle tailgate 90 in the opening direction.

[0032] Referring to FIG. 2, one embodiment of the vehicle 80 may include a
tailgate assist damper 98 coupled to a sidewall 92 of the vehicle 80 and
to the tailgate 90. The tailgate assist damper 98 applies an assist force
to the tailgate 90 in a direction that reduces the force required to be
input by a user to reposition the tailgate 90 between open and closed
positions. In the embodiment depicted in FIG. 2, the tailgate assist
damper 98 applies a force to the tailgate 90 in a direction corresponding
to rotating the tailgate 90 from an open position to a closed position.
Thus, the tailgate assist damper 98 shown in FIG. 2 reduces the opening
speed of the tailgate 90 and/or reduces the force required to be applied
by a user to rotate the tailgate 90 to the closed position. An example of
such a tailgate assist damper 98 includes the Tailgate Lift-Assist
available from Multimatic Inc. of Markham, Ontario, Canada.

[0033] Referring now to FIG. 3, components of the tailgate energy
management system 100 of FIG. 2 are shown in greater detail. The tailgate
assist damper 98 is coupled to the tailgate 90 through a linkage 95 that
connects to a hinge 94. The linkage 95 and the hinge 94 transmit torque
from the tailgate assist damper 98 to the tailgate 90. The rotatable drum
124 of the retractable cable assembly 120 is coupled to the sidewall 92
of the vehicle 80. As depicted in FIG. 3 and shown in greater detail in
FIG. 4, the rotatable drum 124 is mounted to the sidewall 92 with a hub
132 that interfaces with the governor 110. When the electronic control
unit 200 determines the opening speed of the tailgate 90 needs to be
reduced, the governor 110 interacts with the hub 132 to apply a governing
force to the rotatable drum 124, which, in turn, limits the opening speed
of the tailgate 90. In some embodiments, the retractable cable assembly
120 may further include a pre-wound spring 126 that applies a coiling
force to the rotatable drum 124. The coiling force is applied in a
direction that assists with winding the cable 122 about the rotatable
drum 124 as the tailgate 90 rotates from an open position to a closed
position.

[0034] Referring now to FIGS. 2 and 3, by controlling the opening speed of
the tailgate 90, the tailgate energy management system 100 controls a
maximum amount of kinetic energy that the tailgate 90 carries as the
tailgate 90 rotates from a closed position to an open position. By
limiting the amount of kinetic energy carried by the tailgate 90 as it
opens, damage to the tailgate 90 and/or a surrounding object may be
minimized if the tailgate 90 contacts the surrounding object while
opening.

[0035] Specifically, as the tailgate 90 rotates to an open position, the
tailgate assist damper 98 applies torque to the tailgate 90 that
decreases the opening speed of the tailgate 90. Simultaneously, the cable
122 begins to pay out from the rotatable drum 124. The speed sensor 210
senses that the cable 122 is being paid out and transmits a speed signal
to the electronic control unit 200 indicative of the opening speed of the
tailgate 90. In the embodiment depicted in FIGS. 2 and 3, the speed
sensor 210 measures the speed of rotation of the rotatable drum 124.
Because the rotatable drum 124 pays out the cable 122 coupled to the
tailgate 90, the speed of rotation of the rotatable drum 124 corresponds
to the opening speed of the tailgate 90.

[0036] The electronic control unit 200 receives the speed signal from the
speed sensor 210. A processor in the electronic control unit 200
processes the speed signal from the speed sensor 210, and, based on a
computer readable and executable instruction set stored in memory,
determines if the opening speed of the tailgate 90 is approaching a
pre-determined maximum opening speed. The pre-determined maximum opening
speed of the tailgate 90 may be calculated and stored in the memory of
the electronic control unit 200. The maximum opening speed may be
determined such that the kinetic energy of the tailgate 90 does not
exceed a certain threshold of kinetic energy, for example about 10
joules. The opening speed of the tailgate 90 and the weight of the
tailgate 90 determine the kinetic energy of the tailgate 90 as the
tailgate 90 rotates to the open position.

[0037] The electronic control unit 200 compares the speed signal received
from the speed sensor 210 to a stored value to determine whether the
opening speed of the tailgate 90 is approaching or exceeds the
pre-determined maximum opening speed. In some embodiments, the electronic
control unit 200 may include a control variable that is stored in memory
of the electronic control unit 200. The instruction set of the electronic
control unit 200 instruct the processor to compare the speed signal that
is received from the speed sensor 210 to the control variable stored in
memory. In other embodiments, the electronic control unit 200 may include
a lookup table stored in memory that correlates the speed signal
transmitted by the speed sensor 210 to an opening speed of the tailgate
90. In yet other embodiments, the instruction set may include a
conversion variable that correlates the speed signal transmitted by the
speed sensor 210 to an opening speed of the tailgate 90. Thus, the
electronic control unit 200 determines if the opening speed of the
tailgate 90 is approaching a pre-determined maximum opening speed by
comparing the speed signal transmitted by the speed sensor 210 to a
stored value stored within the electronic control unit 200.

[0038] In the embodiment of vehicles 80 where the speed sensor 210 uses a
Hall Effect sensor, the electronic control unit 200 may evaluate the time
intervals between voltage peaks that are induced into the speed sensor
210 by rotating permanent magnets coupled to the retractable cable
assembly 120. The time intervals between voltage peaks measured by the
Hall Effect sensor correspond to the speed of rotation of the permanent
magnets and, in turn, the opening speed of the tailgate 90. In addition,
the electronic control unit 200 may evaluate the speed signal that is
received from the speed sensor 210 to calculate the angular opening speed
of the tailgate 90.

[0039] As the opening speed of the tailgate 90 approaches the maximum
opening speed, the electronic control unit 200 processes the speed signal
from the speed sensor 210 based on the instruction set and determines
that the tailgate 90 is approaching the pre-determined maximum opening
speed. The electronic control unit 200 transmits a control signal to the
governor 110 to actuate the governor 110. The governor 110 receives the
control signal from the electronic control unit 200 and, in turn, applies
a governing force to the tailgate 90. The governing force slows the
opening speed of the tailgate 90. In the embodiment depicted in FIGS. 2
and 3, the governor 110 is coupled to the rotatable drum 124 by the hub
132. The governor 110, therefore, applies the governing force to hub 132
such that the speed of rotation of the rotatable drum 124, and the
corresponding speed that the rotatable drum 124 pays out the cable 122,
is limited. Thus, the governor 110 slows the opening speed of the
tailgate 90.

[0040] In embodiments of the vehicle 80 that include electromechanical
brakes as the governor 110, the electronic control unit 200 may transmit
a control signal to the governor 110 to intermittently apply and release
the electromechanical brake, such that the governing force is "pulsed,"
thereby decreasing the opening speed of the tailgate 90.

[0041] In some embodiments, the tailgate assist damper 98 and the tailgate
energy management system 100 may work in conjunction with one another to
control the opening speed of the tailgate 90. In general, tailgate assist
dampers 98 provide a directional force to tailgates 90 that decreases the
opening speed of the tailgate 90 and reduces the force a user must apply
to rotate the tailgate 90 from an open position to a closed position.
Under normal operating conditions, the tailgate assist damper 98 may
control the opening speed of the tailgate 90 without exceeding a
predetermined maximum opening speed. However, under certain operating
conditions, for example, with the vehicle 80 parked on an incline, at
elevated temperatures, and/or with a worn tailgate assist damper 98, the
tailgate 90 may be prone to open at speeds that exceed the pre-determined
maximum opening speed. Under conditions such as these, the tailgate
energy management system 100 and the tailgate assist damper 98 operate in
conjunction with one another to control the opening speed of the tailgate
90 such that the tailgate 90 opens without intervention from a user, and
opens without exceeding the pre-determined maximum opening speed.

[0042] Conversely, under certain operating conditions, for example, with
the vehicle 80 parked on an incline, the tailgate 90 may be prone to open
at a speed that does not exceed the maximum opening speed. Under such
conditions, the tailgate assist damper 98 will apply torque to the
tailgate 90 that prevents the tailgate 90 from opening at a speed greater
than the maximum opening speed. In these conditions, the speed sensor 210
continues to transmit a speed signal to the electronic control unit 200.
The electronic control unit 200 calculates that the opening speed of the
tailgate 90 and determines that the opening speed of the tailgate 90 is
not approaching the pre-determined maximum opening speed. Because no
governing force is required to slow the opening speed of the tailgate 90
below the pre-determined maximum opening speed, the electronic control
unit 200 does not transmit a control signal to the governor 110 to
actuate the governor 110. Thus, the tailgate energy management system 100
does not apply a governing force to the tailgate 90 to reduce the opening
speed of the tailgate 90.

[0043] Alternatively, or in addition to the tailgate assist damper 98, the
vehicle 80 may include torsion springs (not shown) that apply a direction
force to the tailgate 90. The directional force applied by the torsion
springs is applied to the tailgate 90 is a direction that decreases the
opening speed of the tailgate 90 and reduces the force a user must apply
to rotate the tailgate 90 from an open position to a closed position.

[0044] Another embodiment of a vehicle 80 including a tailgate energy
management system 100 is depicted in FIGS. 5 and 6. In this embodiment,
the tailgate energy management system 100 includes a hub 132 located
within one of the sidewalls 92 of the vehicle 80. In the depicted
embodiment, the hub 132 is coupled to the tailgate 90 with a reduction
gear set 130, a linkage 95, and a hinge 94. The hub 132 is coupled to the
governor 110, allowing the governor 110 to apply the governing force to
the tailgate 90 by applying the governing force directly to the hub 132.

[0045] Similar to the embodiment described with reference to FIGS. 2 and 3
above, the tailgate energy management system 100 depicted in FIGS. 5 and
6 controls a maximum amount of kinetic energy that may be carried by the
tailgate 90 as the tailgate 90 rotates from a closed position to an open
position. The speed sensor 210 transmits a speed signal indicative of the
opening speed of the tailgate 90 to the electronic control unit 200. In
the embodiment depicted in FIGS. 5 and 6, the speed sensor 210 measures
the speed of rotation of one of the members of the reduction gear set
130. Because the reduction gear set 130 is coupled to the tailgate 90 by
the linkage 95 and the hinge 94, the speed of rotation of the members of
the reduction gear set 130 corresponds to the opening speed of the
tailgate 90.

[0046] The electronic control unit 200 receives the speed signal from the
speed sensor 210. The electronic control unit 200 evaluates the speed
signal from the speed sensor 210 to determine if the opening speed of the
tailgate 90 is approaching a pre-determined maximum opening speed. As the
opening speed of the tailgate 90 approaches the maximum opening speed,
the electronic control unit 200 transmits a control signal to the
governor 110 to actuate. The governor 110 receives the control signal
from the electronic control unit 200 and applies a governing force to the
tailgate 90. The governing force slows the opening speed of the tailgate
90. In the embodiment depicted in FIGS. 5 and 6, the governor 110 applies
the governing force to the hub 132, such that the speed of rotation of
the hub 132, and the corresponding speeds of the reduction gear set 130,
are limited. Thus, the governor 110 slows the opening speed of the
tailgate 90.

[0047] Vehicles 80 that include tailgate energy management systems 100 as
described herein may be included with other components that allow the
tailgate 90 to be actuated by a user while the user is positioned at a
location remote from the tailgate 90 and/or the vehicle 80. An example of
such an application is a vehicle 80 that includes a remote keyless entry
system that allows a user to trigger operation of tailgate 90. A vehicle
80 having a remote keyless entry system may allow the user to remotely
rotate the tailgate 90 from a closed position to an open position. By
limiting the maximum kinetic energy that the tailgate 90 may carry as it
opens, the tailgate energy management system 100 may reduce the
likelihood of damage due to contact of the tailgate 90 with any
surrounding object as the tailgate 90 is remotely opened.

[0048] Vehicles 80 that include remote keyless entry systems and tailgate
energy management systems 100 as described hereinabove may include
control logic that disables the remote keyless entry system in the event
that the tailgate energy management system 100 is not reducing the
opening speed of the tailgate 90. In one embodiment, the control logic
may transmit a command to disable the remote keyless entry system from
performing subsequent opening operations if the electronic control unit
200 determines that the opening speed of the tailgate 90 exceeds the
maximum opening speed.

[0049] Additionally, as a user may remove and reattach the tailgate 90
from the vehicle 80, the user may reattach the tailgate 90 to the vehicle
80 without properly connecting the tailgate energy management system 100
to the tailgate 90. The electronic control unit 200 may include control
logic stored in memory that evaluates the opening speed of the tailgate
90. If the tailgate energy management system 100 is not properly
connected to the tailgate 90, the speed sensor 210 may not measure an
opening speed of the tailgate 90 after the tailgate 90 has been triggered
to open by the remote keyless entry system. In the event no opening speed
is measured but an opening operation has been triggered by the remote
keyless entry system, the electronic control unit 200 may disable the
remote keyless entry system from triggering subsequent opening
operations.

[0050] Alternatively, or in addition, in vehicles 80 that include the
tailgate energy management system 100 as depicted in FIGS. 2 and 3, the
electronic control unit 200 may be connected to a retraction sensor (not
shown) that evaluates whether any cable 122 is paid out from the
rotatable drum 124. In general, when connecting the cable 122 to the
tailgate 90, cable 122 may be paid out from the rotatable drum 124. Thus,
if the retraction sensor senses that no cable 122 is paid out (i.e., the
cable 122 is fully wound along the rotatable drum 124), the electronic
control unit 200 may disable the remote keyless entry system from
triggering an opening operation.

[0051] Vehicles 80 may also include a tailgate position sensor (not shown)
that senses if the tailgate 90 is located in a closed position and
transmits a tailgate position signal to the electronic control unit 200.
If the electronic control unit 200 determines that the tailgate 90 is
located in an open position, the electronic control unit 200 may disable
the remote keyless entry system from triggering an opening operation.

[0052] Vehicles 80 that include tailgate energy management systems 100
according to the present disclosure allow a user to manually rotate the
tailgate 90 between open and closed positions without requiring operation
of the tailgate energy management systems 100, such as when the kinetic
energy of the tailgate 90 does not exceed the threshold energy as the
user manually rotates the tailgate 90 between open and closed positions.
Thus, a user may manually open the tailgate 90 of the vehicle 80 without
having to disconnect the tailgate energy management system 100 from the
tailgate 90. Additionally, the tailgate energy management system 100 may
not add significant resistance to rotating the tailgate 90 to the closed
position from the open position. Thus, closing the tailgate 90 by the
user may not be more difficult as compared to a vehicle 80 that does not
include a tailgate energy management system 100.

[0053] It should now be understood that vehicles having tailgates may
include tailgate energy management systems that limit the opening speed
of the tailgates. By limiting the opening speed of the tailgates, the
amount of energy the tailgates carry as they open may be controlled such
that the tailgates cannot impart significant force on surrounding
objects. The tailgate energy management systems apply governing forces to
the tailgates that control opening speed of the tailgates while allowing
a user to manually open and close the tailgate of the vehicle. The
tailgate energy management systems may work in conjunction with tailgate
assist dampers, which assist both with opening and closing tailgates.

[0054] It is noted that the terms "substantially" and "about" may be
utilized herein to represent the inherent degree of uncertainty that may
be attributed to any quantitative comparison, value, measurement, or
other representation. These terms are also utilized herein to represent
the degree by which a quantitative representation may vary from a stated
reference without resulting in a change in the basic function of the
subject matter at issue.

[0055] While particular embodiments have been illustrated and described
herein, it should be understood that various other changes and
modifications may be made without departing from the spirit and scope of
the claimed subject matter. Moreover, although various aspects of the
claimed subject matter have been described herein, such aspects need not
be utilized in combination. It is therefore intended that the appended
claims cover all such changes and modifications that are within the scope
of the claimed subject matter.